The present invention relates to a two-side image forming apparatus capable of automatically copying mixed documents including one-sided and two-sided documents onto the front and rear sides of transfer sheets.
In the case of a conventional two-sided image forming apparatus having an automatic document feeder, copying operations are carried out in the following manner: When a large number of documents are to be continuously copied, an operator checks whether they are one-sided or two-sided documents. Then, the operator selects either a one-sided or a two-sided mode. After that, a copy start command is given to the apparatus.
Accordingly, in the case where mixed documents including one-sided and two-sided documents are continuously copied with the image forming apparatus, it is necessary for the operator to previously sort the documents into one-sided and two-sided ones, and then the operator designates the copy mode for each of the one-sided and two-sided documents so as to carry out a copying operation. Therefore, the copying operation is very inefficient.